What do today's teens call someone they think of as clumsy and strupid?

Freak.

Weirdo.

Retard.

Us teens don't really get that deep and descriptive while talking.

Ok, firstly, you're making a judgment on 'teens' by just some kids you saw outside of a library. There will always be the kids who do stupid things and get themselves in trouble. Their way of coping with it, is being idiots about it. I bet when you were a teen there were kids just like that, so don't go grouping it with just 'teens' these days, because regardless; some are just that way. Another thing, not all teens are like that. Stealing isn't cool, and some people do it because they can't afford to buy it. So instead of telling their friends that, they say that it's cool. Not that it's any excuse, of course. But it's not just because stealing is 'cool'. Lastly, you can get kicked out of places as a teen for various reasons. You don't even really have to do anything. Granted, some are just obviously wanting to get into trouble. But others who make mistakes, get the punishments because of those people. So don't go grouping all of them together because it's unfair, and inaccurate.

i think that depends where you come from, i'm from the uk and we would use words like

idiot

fool

daft bugger

dosy

twit

numpty (in scotland)

and in america

knucklehead

idiot

douche

nincompoop (my personal favourite one)

i hope this is of some help :-)

Haaha well I'm clumsy and stupid and my friends call me a douche soo hope that helps :)

I can think of a couple of examples.

Klutz

Dork

"Dork" was the first thing that came to mind reading that.

Well usually an idiot

fool :p